Buckle propagation in pipelines with non-uniform thickness   总被引：1，自引：0，他引：1  

Jianghong  Michelle S.   《Ocean Engineering》2001,28(10)

Finite element solutions for the steady-state buckle propagation pressure in a pipeline with non-uniform thickness are given. The results are useful in finding buckle propagation pressures in corroded pipelines. It has been found that when corrosion is equal to or less than 10% of the original pipeline thickness, the pipeline collapses in an overall shell buckling mode; otherwise, the pipeline experiences local buckling. The propagation pressure decreases with both the thickness and angular extent of the reduced section, but the rate of decrease with thickness reduction is almost independent of the angular extent of corrosion when it is greater than 90°.  相似文献   

Why Web GIS May Not Be Enough: A Case Study with the Virtual Research Vessel     

Dawn J. Wright  Elizabeth O'Dea  Judith B. Cushing  Janice E. Cuny  Douglas R. Toomey 《Marine Geodesy》2003,26(1):73-86

During several decades of investigation, the East Pacific Rise seafloor-spreading center at 9°-10°N has been explored by marine geologists, geophysicists, chemists, and biologists, and has emerged as one of the best studied sections of the global midocean ridge. It is an example of a region for which there is now a great wealth of observational data, results, and data-driven theoretical studies. However, these have yet to be fully utilized, either by research scientists or educators. While the situation is improving, a large amount of data, results, and related theoretical models still exist either in an inert, noninteractive form (e.g., journal publications) or as unlinked and currently incompatible computer data or algorithms. Presented here is the prototype of a computational environment and toolset, called the Virtual Research Vessel, to improve the situation by providing marine scientists and educators with simultaneous access to data, maps, and numerical models. While infrastructure is desired and needed for ready access to data and the resulting maps via web GIS in order to link disparate data sets (data to data), it is argued that data must also be linked to models for better exploration of new relations between observables, refinement of numerical simulations, and the quantitative evaluation of scientific hypotheses. For widespread data access, web GIS is therefore only a preliminary step rather than a final solution, and the ongoing implementation of the Virtual Research Vessel (scheduled for final completion in 2004-2005) is a case study for the midocean ridge community to test the effectiveness of moving beyond the data-to-data mode towards data-to-models and data-to-interpretation.  相似文献   

The morphology and structure of the West O’Gorman Fracture Zone     

James S. McClain  Mona A. Wright 《Marine Geophysical Researches》1990,12(4):317-328

The West O’Gorman Fracture Zone is an unusual feature that lies between the Mathematician Ridge and the East Pacific Rise on crust generated on the East Pacific Rise between 4 and 9 million years ago. We made a reconnaissance gravity, magnetic and Sea Beam study of the zone with particular emphasis on its eastern (youngest) portion. That region is characterized by an elongate main trough, a prominent median ridge and other, smaller ridges and troughs. The structure has the appearance of large-offset fracture zone, possibly in a slow spreading environment. However, magnetic anomalies indicate that the offset, if any, is quite small, and the spreading rate during formation was fast. In addition, the magnetic profiles do not support earlier models for a difference in spreading rate north and south of the fracture. The morphology of the fracture zone suggests that flexure may be responsible for some of the topography; but gravity studies indicate some of the most prominent features of the fracture zone are at least partially compensated. The main trough is underlain by a thin crust (or high density body), similar to large-offset fracture zones in the Atlantic, while the median ridge is underlain by a thickened crust. Sea Beam data does not unambiguously resolve between volcanism or serpentinization of the upper mantle as a mechanism for isostatic compensation. Why the West O’Gorman exists remains enigmatic, but we speculate that the topographic expression of a fracture zone does not require a transform offset during formation. Perhaps the spreading ridge was magma starved for some reason, resulting in a thin crust that allowed water to penetrate and serpentinize portions of the upper mantle.  相似文献   

The effects of heavy metals on the primary productivity in the marine ecosystem enclosures     

Chen Qihuan  Wu Shengsan  Zhuang Liangzhong  Heather Dovey 《海洋学报(英文版)》1988,7(4):630-630

In April, 1985, scientists from China and Canada made a marine enclosed ecosystem experiment cooperatively in Xiamen. The experiment was carried out in the plastic bags in a shorebased tank. To the bags, heavy metals (Cu, Hg, Zn, Pb and Cd) were added quantitatively and their effects on the primary productivity were studied. The results show that the effects of low level metal mixture (Cu 3.5-10.0, Hg 0.2-1.0, Pb 0.3-1.5, Zn 3.5-17.5,  相似文献   

Effect of temperature and food availability on reproductive investment of first-time spawning male Atlantic cod, Gadus morhua     

Yoneda  Michio; Wright  Peter J. 《ICES Journal of Marine Science》2005,62(7):1387-1393

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A synthesis of the early life history of the anglerfish, Lophius piscatorius (Linnaeus, 1758) in northern British waters   总被引：1，自引：0，他引：1  

Hislop  John R.G.; Gallego  Alejandro; Heath  Michael R.; Kennedy  Fiona M.; Reeves  Stuart A.; Wright  Peter J. 《ICES Journal of Marine Science》2001,58(1):70-86

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Modelling hydrographic changes in the Labrador sea over the past five decades     

Youyu Lu  Daniel G. Wright  Igor Yashayaev 《Progress in Oceanography》2007,73(3-4):406

Inter-annual to inter-decadal changes of hydrographic structure and circulation in the subpolar North Atlantic are studied using a coarse resolution ocean circulation model. The study covers 1949 through 2001, inclusive. A “time-mean state nudging” method is applied to assimilate the observed hydrographic climatology into the model. The method significantly reduces model biases in the long-term mean distribution of temperature and salinity, which commonly exist in coarse-resolution ocean models. By reducing the time-mean biases we also significantly improve the model’s representation of inter-annual to inter-decadal variations. In the central Labrador Sea, the model broadly reproduces the heat and salt variations of the Labrador Sea Water (LSW) as revealed by hydrographic observations. Model sensitivity experiments confirm that the low-frequency hydrographic changes in the central Labrador Sea are closely related to changes in the intensity and depth of deep convection. Changes in surface heat flux associated with the winter North Atlantic Oscillation (NAO) index play a major role in driving the changes in T–S and sea surface height (SSH). Changes in wind stress play a secondary role in driving these changes but are important in driving the changes in the depth-integrated circulation. The total changes in both SSH and depth-integrated circulation are almost a linear combination of the separate influences of variable buoyancy and momentum fluxes.  相似文献   

Morphology and Evolution of the Remnant Colville and Active Kermadec Arc Ridges South of 33°30′ S     

Wright  Ian C. 《Marine Geophysical Researches》1997,19(2):177-193

Swath MR1 data from the remnant Colville and active Kermadec arc margins, south of 33°30 S (SW Pacific), record the structural morphology and evolution of the rifted, and now separate portions, of the proto-Colville–Kermadec arc flanking the actively widening southern Havre Trough back-arc basin associated with Pacific-Australian plate convergence. Both the remnant Colville and active Kermadec arc margins comprise opposing, asymmetric, partially basement exposed, segmented ridges. Differences in morphology between the two ridges are, however, observed. The single, near linear, border fault system, with relief of 1000 m, along the western edge of the Kermadec margin is interpreted to be the exposed fault escarpment of a major, west-dipping, detachment fault. In contrast, two major zig-zag border fault systems along the eastern edge of the Colville Ridge, bounding a back-tilted ridge flank terrace, are interpreted as major antithetic faults between the remnant arc and back-arc region. This contrast in structural morphology coincides with, respectively, lesser and greater degrees of both active tectonism and channel-canyon erosion, on the remnant Colville and active Kermadec margins. These differences are interpreted to reflect the progressive trenchward collapse and associated greater rift flank uplift and incisive erosion of the Kermadec foot-wall contrasting with the non-collapse and relatively lesser rift flank uplift and ridge erosion of the Colville hanging-wall. The data provide further constraints on the early evolution of the Havre Trough in particular, and back-arc basins in general.  相似文献   

THE RISE AND FALL OF THE PORT OF KAIPARA     

L. W. Wright 《New Zealand geographer》1969,25(1):61-67

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A radiation model for the vela pulsar     

J. Davila  C. Wright  G. Benford 《Astrophysics and Space Science》1980,71(1):51-63

We model the Vela emission in radio, optical and gamma wavelengths. We assume that radio emission occurs near the polar axis deep in the magnetosphere. Optical and gamma radiation arises through ordinary synchrotron mechanisms in a wide hollow cone, near the light cylinder. Fitting of observed frequencies and luminosities in the gamma and optical give reasonable plasma parameters, and indicate that field-plasma pressure balance breaks down before the light cylinder, as required by the picture. Some optical coherence is necessary if we attribute both radio and optical emission to the same species of particles, with 100, but it is not required otherwise. Gamma-ray pulses arise from 10⁵ electrons. We suggest a single-pole orthogonal rotor picture which might account for the Vela pulse phases.  相似文献